A valve driving apparatus which drives an exhaust valve by using electromagnetic force is already known, as disclosed in Japanese Laid-Open Patent Application No. 10-18819 or No. 10-18820. An armature is coupled with an electromagnetic valve (or called exhaust valve) which is provided in this valve driving apparatus. On the upper side of the armature, the first electromagnet and an upper spring are deposited, and on the lower side of the armature, the second electromagnet and a lower spring are deposited. The armature is held at the neutral position in the middle between the first and second electromagnets by the forces of the upper and lower springs. The electromagnetic valve is full closed when the armature touches the first electromagnet, and the electromagnetic valve is full open when the armature touches the second electromagnet. In the above-mentioned valve driving apparatus, the exhaust valve is held at the full closed position by the fact that a predetermined exciting current is supplied to the first electromagnet and the armature is attracted by the first electromagnet. When the supply of the exciting current to the first electromagnet is cut, the armature is pushed by the upper spring and the exhaust valve begins to move in the opening direction. If a predetermined exciting current is supplied to the second electromagnet when the exhaust valve is positioned at a predetermined position, a damping of displacement amplitude by friction of the exhaust valve or remaining pressure of combustion is supplemented and the exhaust valve reaches the full open position by the fact that the electromagnetic force is supplied to the armature in the opening direction.
If the exhaust valve is moving at a high speed when the exhaust valve arrives at the full open position, that is, the armature touches the second electromagnet, such problems as increasing of activating noise of the exhaust valve or bouncing back of the exhaust valve occur. Therefore, in the aforementioned valve driving apparatus, the speed of the exhaust valve is restrained when the exhaust valve approaches to the full open position, by reducing the exciting current to the second electromagnet when the exhaust valve reaches near the full open position.
Incidentally, in the internal combustion engine installed on a vehicle, when an accelerator pedal is disengaged during the high speed driving, for example, a fuel injection cut control for stopping a fuel injection to a combustion chamber of the engine is executed. Because combustion does not occur in the process of the fuel injection cut control, the pressure in the combustion chamber of the engine is negative (or called vacuum) when the exhaust valve is at the opening timing, that is, a piston of the engine is near bottom dead center. This negative pressure forces the exhaust valve in the opening direction. Consequently, if the same value of the exciting current is supplied to the second electromagnet in the execution of the fuel injection cut control, the armature touches the second electromagnet at the higher speed. Consumed electric energy increases, because it is necessary to supply the exciting current again to pull the armature back to the second electromagnet in order to prevent the armature from bouncing back. Furthermore, a large noise occurs by the high speed collision between the armature and the second electromagnet.